Finely divided particles of iron and ferric oxide blown up during the iron and steel making process, for example, in a smelting furnace or the like are generally collected by a dust collector as dust. This kind of dust (hereinafter referred to as “steelmaking dust”) contains iron and ferric oxide as a principal component and, therefore, the reuse thereof is desirable. However, since the steelmaking dust is made up of finely divided particles, the finely divided particles may scatter and blow upwards in the smelting furnace, when such finely divided particles are charged directly into the smelting furnace, and most of the finely divided particles may be subsequently collected again in the dust collector, resulting in reduction in efficiency with which the steelmaking dust can be reused. For this reason, it has hitherto been quite often to dispose most of steelmaking dust in reclaimed lands, but considering that the steelmaking dust generated in Japan amounts to hundred thousands of tons per year, disposal by filling up in land is not desirable in terms of not only the availability of reclamation sites and the effective utilization of resources, but the destruction of the environment.
In view of the foregoing, various attempts have hitherto been made to reuse the steelmaking dust. For example, the Japanese Laid-open Patent Publication No. 11-152511 discloses formation of the steelmaking dust into pellets of about 2 to 15 mm in diameter and charging the resultant pellets into an electric furnace to recover ferric oxides during the course of the hot metal process.
The Japanese Laid-open Patent Publication No. 9-316512 discloses briquetting of the steelmaking dust, in which thermoplastics is added and the Japanese Laid-open Patent Publication No. 2002-194449 discloses briquetting of the steelmaking dust and grinding sludge, in which a solidification accelerating agent is added.
Although in the pellet forming method disclosed in the first mentioned patent document, the handling is easy in charging the recovered dust into the electric furnace in view of the dust having been palletized, the efficiency of charging into the electric furnace is problematic since the pellets so formed have a relatively small size.
The method disclosed in each of the second and third mentioned patent documents, in which the additive is used, is an effective means of forming solid briquettes, but a problem has been found in that the addition of the additive such as plastics or binders tends to render the process to be complicated and costly. Also, it is not desirable since the additive used tends to constitute a cause of environmental load.